Polymer beads and method for preparation thereof

ABSTRACT

The present invention relates to a process for producing polymer beads incorporating solid particles and to the novel polymer beads per se. The invention provides a process for producing polymer beads incorporating solid particulate material, which process comprises producing a dispersion having a dispersed phase including one or more monomers also including solid particulate material, and causing said one or more monomers to undergo a polymerization reaction to form said polymer beads, wherein said dispersion further includes a solid phase dispersing agent for dispersing solid particles of material in the dispersed phase and wherein said solid phase dispersing agent reacts with at least one monomer to thereby become chemically incorporated in said polymer. The polymer beads comprise a polymer matrix having solid particulate material dispersed substantially uniformly therein and wherein the polymer matrix incorporates a solid phase dispersing agent chemically reacted into the polymeric matrix.

This application is the national phase of International applicationPCT/AU95/00582 filed Sep, 8, 1995 which designated the U.S.

The present invention relates to a process for producing polymer beadsincorporating solid particles. The polymer beads produced by the processof the present invention are particularly suitable for use as ionexchange resins. The invention further relates to the polymeric beadsand to ion exchange resins incorporating the polymeric beads.

Ion exchange is widely used a technique for removing contaminants fromwater. Ion exchange techniques involve passing water through a packedbed or column of ion exchange resin. Contaminant materials are adsorbedonto the ion exchange resin. Ion exchange resins are particularlysuitable for removing contaminants from water.

Crosslinked polymer beads that are physically like ion exchange resinsbut without the ion-exchanging functional groups are also capable ofadsorbing organic contaminants from water; one such resin used for thispurpose is XAD resin. Some of the contaminant removal capacity of ionexchange resins observed in practice may be due to adsorption by thepolymeric matrix of the resin.

For ease of handling in use, the above crosslinked polymer beads with orwithout ion exchange functionality should be substantially spheroidal orellipsoidal in form, ideally they should be substantially uniform insize and free of very small particles. This enhances the flow propertiesof the dry resin or a concentrated suspension in water so that the resincan be metered or pumped. Such beads can be made by polymerisation of adispersed monomer phase.

In addition, resin containing dispersed particulate material may enhancethe case of separation either by increasing the density of the resinbead or by providing another property such as magnetic susceptibilitywhich can be used to separate the resin from the water. Resinsincorporating magnetic particles flocculat and settle rapidly bymagnetic attraction. Such particulate material should be incorporatedinto the resin bead in a manner that prevents its loss by erosion ordissolution during use. It is highly desirable that the particulatematerial should be dispersed evenly throughout the polymer bead.Improved mechanical strength is a further benefit of even particulatedispersion. This had been difficult to achieve until now.

Processes for the manufacture of magnetic ion exchange resins have beendescribed in some prior art patents. For example, U.S. Pat. No.2,642,514 assigned to American Cyanamid Company, discloses an ionexchange process using a mixed ion exchange resin. One of the ionexchange resins is a magnetic resin. The magnetic resin is produced bypolymerising a reagent mix until a viscous syrup is obtained. Magnetiteis added to the viscous syrup and the mixture is agitated to mix in themagnetite. The mixture is cured to form a hard resin that issubsequently ground to form irregular particles of magnetic resin.

European Patent Application No. 0,522,856 in the name of BradtechLimited also discloses the manufacture of magnetic ion exchange resinsby grinding or crushing a polymer having magnetite dispersed throughoutthe polymer matrix. The processes for producing magnetic ion exchangeresins disclosed in U.S. Pat. No. 2,642,514 and EP 0,522,856 require agrinding step, which increases the cost and complexity of the processand increases losses due to the formation of polymer particles outsidethe desired particle size range during the grinding step.

An alternative process for producing magnetic ion exchange resins isdescribed in Australian Patent Application No. 60530/80 in the name ofICI Australia Ltd. In this process, magnetic porous crosslinkedcopolymer particles are produced by a dispersion polymerisation process.A mixture of polymerizable vinyl compounds, magnetic powder,polymerisation initiator and suspension stabilizer is dispersed in waterand polymerised.

A similar process for producing magnetic ion exchange resins isdescribed in Japanese Patent Application No. 62141071 in the name ofMitsubishi Chemical Industries K.K. In this process it is preferred toadd an electron donor substance such as polyvinyl pyridine-styrenecopolymer, polyacrylamide-styrene copolymer or polyvinyl imidazolecopolymer to the mixture in order to stabilise the dispersion ofmagnetic powder. According to the patent, the dispersion treatment isimportant for stabilising the dispersed state so that the rate ofsettling of the magnetic powder is reduced by breaking up magneticparticles which have clumped together in secondary or larger particlesinto primary particles. Furthermore, it is necessary to use dispersionequipment which differs from normal mixing equipment, with specialmixers being required.

The suspension stabiliser described in the ICI Australia Ltd. patentapplication and in the Mitsubishi Chemical Industries K.K. patentapplication are not capable of reacting with the monomers used to formthe resins and do not become chemically incorporated into the resin.

Experiments by the present inventors using the process described in JP62-141,071 showed that use of a polyvinyl pyridine-styrene copolymer,when used as a dispersing that use of a polyvinyl pyridine-styrenecopolymer, when used as a dispersing agent in a system containing 10.8%γ-Fe₂ O₃ in a glycidyl methacrylate/divinyl benzene copolymer system,gave resin beads that encapsulated the magnetic oxide. However, thebeads were irregular in shape, very polydisperse in size, poor inmechanical strength, had a relatively low loading of magnetic oxidewhich was poorly dispersed in the beads.

It is an object of the present invention to provide an improved processfor manufacturing polymer beads incorporating solid particles.

FIGS. 1A, 1B, 2A, 2B, 3A, 3B and 3C are all photomicrographs of polymerbeads incorporating solid particles.

In a first aspect, the present invention provides a process forproducing polymer beads incorporating solid particulate material, whichprocess comprises producing a dispersion having a dispersed phaseincluding one or more monomers also including solid particulatematerial, and causing said one or more monomers to undergo apolymerisation reaction to form said polymer beads, wherein saiddispersion further includes a solid phase dispersing agent fordispersing solid particles of material in the dispersed phase andwherein said solid phase dispersing agent reacts with at least onemonomer to thereby become chemically incorporated in said polymer.

The present invention provides a process which can produce polymer beadsin which solid particulate material is evenly distributed throughout thepolymer beads.

In a preferred embodiment of the present invention, an organic phase isthe dispersed phase and, for convenience, the invention will hereinafterbe described with reference to the organic phase being the dispersedphase. However, it will be appreciated that the invention alsoencompasses an aqueous phase being the dispersed phase, in which casewater soluble monomers are used to produce the polymer beads.

Where an organic phase constitutes the dispersed phase, an oil-in-waterdispersion is produced. The organic phase includes one or more monomersthat react to form the polymer matrix of the polymer beads. It isespecially preferred that the polymer matrix be a copolymer, whichrequires two (or more) monomers to be used. The polymer beads may haveion exchange properties and it is particularly preferred that theprocess provides for the production of ion exchange resins. Generallyion exchange resins require two types of monomers:

(a) monomers which are able to provide crosslink points; and

(b) monomers which are able to provide functional groups.

Of course, the polymer chain may be a copolymer and the functionalgroups may be added by later reaction of one of the polymer monomerresidues in the polymer resin. Accordingly, when the polymer beads areto be used as an ion-exchange resin, the organic phase should include acrosslinking monomer and a functional monomer that provides thenecessary functional groups to give the polymer an ion-exchangecapability or provides sites that may be later reacted to provide therequired functional groups to confer ion-exchange capability to thepolyer. Other monomers may be able to be included in the organic phaseto copolymerise with the crosslinking monomer and the functionalmonomer, for example, a backbone monomer may be included.

The cross-linking monomer may be selected from a wide range of monomers,including divinyl monomers such as divinyl benezene, ethyleneglycoldimethacrylate or poly(ethyleneglycol) dimethacrylate or methylenebisacrylamide, ethyleneglycol divinylether and polyvinyl ester compoundshaving two or more double bonds. This list is not exhaustive.

A wide range of functional monomers may also be used in the process ofthe present invention. Suitable monomers include glycidyl methacrylate,vinyl benzyl chloride, dimethylaminoethyl methacrylate,N,N-dimethylaminopropyl acrylamide and methacrylamide, vinyl pyridine,diallylamine, and their quaternized derivatives. N-vinyl formamide andits hydrolized derivative, and methyl acrylate and its derivatives. Thislist is not exhaustive.

The backbone monomers include any monomer polymerizable by free radicalssuch as styrene, vinyl toluene, methylmethacrylate and other acylatesand methacrylates. This list is not exhaustive.

In order to increase the efficieny of removal of contaminants from waterbeing treated by the polymer beads, it is preferred that the polymerbeads are macroporous. This increases the total surface are of each beadavailable for contact. To produce macroporous polymer beads according tothe present invention, the dispersed phase should include one or moreporogens. The porogen becomes dispersed throughout the droplets thatform the dispersed phase, but that porogen does not take part in thepolymerisation reaction. Accordingly, after the polymerisation reactionis completed, the porogen can be removed from the polymer beads, forexample by washing or steam stripping, to produce macroporosity in thepolymer beads.

Suitable porogens for use in the process of the present invention inwhich the organic phase is the dispersed phase include aromaticcompounds such as toluene and benzene, alcohols such as butanol,iso-octanol, cyclohexanol, dodecanol, isoamyl alcohol and methyliso-butyl carbinol, esters such as ethyl acetate and butyl acetate,saturated hydrocarbons such as n-heptane, iso-octane, halogenatedsolvents such as dichloroethane and trichloroethylene, plasticisers suchas dioctylphthalate and dibutyl adipate, polymers such as polystyreneand polyvinyl acetate; and mixtures thereof. Mixtures of cyclohexanolwith other porogens such as dodecanol or toluene have been found to beespecially suitable for use as a porogen in the process of the presentinvention. It will be appreciated that the above list of porogens is notexhaustive and that the invention encompasses the use of other porogensand other combinations of porogens.

In one embodiment, incorporation of the solid particulate material intothe polymer beads preferably results in the beads having a higherdensity than they otherwise would have if the solid particulate materialwas not present. As the polymer beads have increased density, settlingtime of the beads is decreased which allows for simpler separation ofthe beads from a water sample being treated. The solid particulatematerial may be described as a weighing agent and assist in promotingrapid settling of the polymer beads.

In one embodiment, the solid particulate material used in the presentinvention may be of any material that has a density higher than thedensity of the polymer material in the absence of the solids. The solidparticulate material is preferably not soluble in water or in anysolution or liquid to be treated by contact with the polymer beads. Itis also preferred that the solid particulate material does not reactwith solution or liquid to be treated.

Some examples of suitable solid particulate material include titania,zirconia, barite, cassiterite, silica, aluminosilicates, nickel oxide,copper oxide, zinc oxide, zinc sulphide, and other oxides, sulphides,sulphates and carbonates of heavy metals.

In an especially preferred embodiment, the solid particulate material isa magnetic material. Incorporation of a solid particulate magneticmaterial into the polymer beads results in the beads becoming magnetic.Magnetic separation techniques may be used to conveniently separate thebeads from a solution or liquid being treated. The solid particulatemagnetic material used in this embodiment of the present invention mayalso be any solid material that is magnetic. Examples include γ-ironoxide (γ-Fe₂ O₃, also known as maghemite), magnetite (Fe₃ O₄), chromiumdioxide, other metal oxides and more exotic magnetic materials, such asthose based on niobium and other rare earth materials. Maghemite isespecially preferred because it is inexpensive.

The solid particulate material is added in the form of particles. Theparticle size of the particles may range up to a size that is up toone-tenth of the particle size of the polymer beads formed in theprocess of the present invention. Particles that are larger than thatmay be difficult to evenly disperse into the polymer beads. Morepreferably, the particles of solid material range in size fromsub-micron (e.g. 0.1 μm) to 500 μm, most preferably from 0.1 μm to 10μm.

The process of the present invention includes a solid phase dispersingagent in the dispersed phase. The solid phase dispersing agent acts todisperse the solid material in the droplets of the dispersed phase tothereby form a stable dispersion (or suspension) of the solid particlesin the dispersed phase and the solid phase dispersing agent reacts withone or more of the monomers to become chemically reacted into thepolymer matrix. Both of these actions are necessary for the effectivedispersal of the solid particulate material in the polymer beads. Use ofa suitable solid phase dispersing agent results in polymer beads beingformed in which the solid particulate material is evenly dispersedthroughout the polymer bead and the solid phase dispersing agent ischemically reacted with the polymer matrix. This avoids, or at leastalleviates, the problem of leaching of the solid particulate materialfrom the polymer beads. This avoids, or at least alleviates, the problemof erosion of the solid particulate material from the polymer beads inservice, as may happen if the solid material was located only on theouter surface of the beads. Selection of the solid phase dispersionagent will depend upon the particular solid material being used and themonomers being used. The solid phase dispersing agent should have a goodaffinity for the surface of the solid material and be able to react withone or more of the monomers.

As one example, a silane methacrylate is a suitable solid phasedispersing agent for use with titania or zirconia particles.

Persons skilled in the art should be readily able to select a desiredsolid phase dispersing agent for the specific reaction system employed.

The polymerisation reaction taking place in the process of the presentinvention is a suspension polymerisation reaction and techniques knownto those skilled in the art to control and monitor such suspensionpolymerisation reactions apply to the present invention. In order tomaintain the dispersed phase in the form of a suspension of droplets inthe continuous phase whilst avoiding aggregation of the droplets, astabilising agent is preferably used. Where the dispersed phase is theorganic phase, the stabilising agent may be polyvinyl alcohol, gelatine,methyl cellulose or sodium polyacrylate. It is to be understood that theinvention extends to cover any stabilising agent that may be suitablefor use. The stabilising agent is typically present in an amount of 0.01to 5.0% by weight, and preferably 0.05 to 2.0% by weight, based on theweight of the whole mixture.

It will also be generally necessary to use an initiator to initiate thepolymerisation reaction. The initiator to be used depends upon themonomers present in the reaction mixture and the choice of initiator andthe amount required will be readily apparent to the skilled addressee.By way of example only, suitable initiators include azoisobutyronitrile,benzoyl peroxide, lauroyl peroxide and t-butyl hydroperoxide. The amountof initiator used is generally in the range of 0.01 to 5.0 wt %, morepreferably 0.10 to 1.0%, calculated on the total weight of monomer(s).

In a preferred embodiment of the present invention, the monomer mixturemay include a functional monomer present in an amount of from 10 to 99%by weight, based upon the weight of total monomers, more preferably 50to 90% by weight (same basis). The crosslinking monomers may be presentin an amount of from 1 to 90% by weight, based on the weight of totalmonomers, more preferably 10 to 50% by weight (same basis). Additionalmonomers may be present in an amount of 0 to 60% by weight, morepreferably 0 to 30% by weight, based on the weight of total monomers.The total monomers may constitute from 1.0 to 50%, more preferably 5.0to 30% by weight of the whole suspension polymerisation mixture.

The solid particles of material are preferably added in an amount offrom 10 to 300 wt %, based on the weight of total monomers, morepreferably 20 to 100% by weight (same basis). The solid phase dispersingagent is preferably added in an amount of 0.10 to 30.0% by weight, morepreferably 1.0 to 10.0% by weight, based on the weight of solidparticles of material.

The dispersion of the dispersed phase (which includes the monomer(s)) inthe continuous phase is usually achieved by mixing the organic andaqueous phases and shearing the resulting mixture. The shear applied tothe dispersion can be adjusted to control the size of the droplets ofthe dispersed phase. As the droplets of dispersed phase are polymerisedto produce the polymer beads, the shear applied to the dispersionlargely controls the particle size of the polymer beads. Generally, thepolymer beads are controlled to have a particle size in the range of10-5000 μm.

Once a stable dispersion of dispersed phase in continuous phase isestablished, the polymerisation reaction is started by heating thedispersion to the desired reaction temperature. The dispersion may beheld at the desired reaction temperature until the polymerisationreaction is substantially complete.

Once the polymerisation reaction is substantially complete, the polymerbeads may be optionally treated to activate the active sites in thepolymer for ion exchange and the beads recovered. The activation of theactive sites in the polymer for ion-exchange will be dependent on thenature of the species to be separated from solution. For example,hydrolysis of poly(ethyl acrylate) beads will provide a weak acid cationion exchange resin suitable for separating transition metal ions such ascadmium and zinc from solution. Amination or quaternization of thepolymer beads may be used to provide an ion exchange resin suitable forthe removal of acidic organic materials from solution. It will be clearto those skilled in the art that the means for activation of the ionexchange sites may be conveniently selected dependent on the nature ofthe compounds to be separated from solution. The beads may requirecleaning before use. This may be achieved by a sequence of washing thebeads or by steam stripping the beads.

One method for cleaning the polymer beads includes the following steps:

(a) add reaction to a large excess of water, stir and allow to settle;

(b) separate beads from the supernatant;

(c) add seperated beads to a large excess of water, stir and allow tosettle before separating beads from the supernatant;

(d) repeat step (c) several times; (e) disperse water washed beads inalcohol (ethanol); (f) separate beads from alcohol and dry.

An alternative clean-up procedure is to steam strip the porogens andthen wash the polymer beads to remove any free solid particulatematerial.

The present invention provides a process which produces polymer beads inwhich solid particulate material is evenly distributed throughout thepolymer beads. In an especially preferred embodiment of the invention, amagnetic polymer bead is produced. The polymer is formed as a copolymerof glycidyl methacrylate and divinyl benzene. The monomers are presentin the organic phase, which also includes a mixture of cyclohexanol withtoluene or dodecanol as porogens. Polyvinyl alcohol is used as astabilising agent. A free radical initiator such as "VAZO" 67 orAzoisobutyronitrile (AIBN) is added to the organic phase as apolymerisation initiator and γ-iron oxide is the magnetic material. Thesolid phase dispersing agent preferred for use in this system is a blockcopolymer of poly(hydroxystearic acid) and poly(ethyleneimine) and soldunder the trade name SOLSPERSE 24000. This solid phase dispersing agenthas a high affinity for the surface of the γ-iron oxide and also reactswith the epoxy group of the glycidyl methacrylate through its primaryand secondary amino groups and then the vinyl groups from themethacrylate react with polymersing radicals to become covalently boundto the polymer matrix. All of the components of the organic phase arepreferably pre-mixed in a separate tank and dispersed in water in thereaction tank.

In another aspect, the present invention provides a process whichproduces polymer beads which incorporates a toughening agent. Thetoughening agents are selected to increase the impact resistance of thepolymer. The general techniques for increasing the toughness of polymerbeads prepared in accordance with the present invention may readily beemployed to produce bead with increased durability. For example, rubbertoughening agents may be used in improve the strength and durability ofstyrene-based polyer beads. The use of these rubber toughening agentsnot only results in improved durability but increases the serviceablelife of the polymer beads. The rubber toughening agents include lowmolecular weight rubbers which may be incorporated into the dispersedphase. A particularly preferred rubber toughening agent is sold underthe trade designation Kraton D1102 although other commercially availablerubber toughening agents are available.

In another aspect, the present invention provides polymer beadscomprising a polymer matrix having solid particulate material dispersedsubstantially uniformly therein and wherein the polymer matrixincorporates a solid phase dispersing agent chemically reacted into thepolymeric matrix.

The polymer beads are preferably macroporous. The particle size of thepolymer beads is preferably within the range of 30 μm to 100 μm. Theparticles of solid material may have a particle size in the range ofsub-micron (e.g. 0.1 μm) to 500 μm and more preferably from 0.1 μm to 10μm.

The solid particulate material may act to increase the density, andhence the weight of the polymer beads. Examples of solid particulatematerials suitable for use in the present invention include titania andzirconia.

In an especially preferred embodiment, the solid particulate material isof a magnetic material and accordingly the polymer beads will bemagnetic.

The solid phase dispersing agent is a chemical compound or species thatcan react with the monomers used to produce the polymeric matrix suchthat the solid phase dispersing agent is incorporated into the polymericmatrix. Further, the solid phase dispersing agent should have a goodaffinity for the surface of the solid particles and preferably should beable to chemically bond to the surface of the solid particles. The useof such agent allows the solid particles to be dispersed throughout thepolymeric matrix.

As the solid particles are dispersed throughout the polymer beads of thepresent invention, the solid particles are not easily removed from thebeads and this allows the beads to be subjected to a number of handingoperations, such as conveying, pumping and mixing, without substantiallyerosion of solid particles therefrom.

In another aspect, the present invention provides polymer beadscomprising a polymeric matrix having solid particulate materialdispersed therein, wherein the polymeric matrix incorporates a solidphase dispersing agent which is chemically reacted into the polymermatrix and wherein the polymer beads incorporate a toughening agent.

The invention further provides ion exchange resins including polymericbeads in accordance with the present invention.

Throughout this specification and the claims which follow, unless thecontext requires otherwise, the word "comprise", or variations such as"comprises" or "comprising", will be understood to imply the inclusionof a stated integer or group of integers but not the exclusion of anyother integer or group of integers.

The invention will be further described with reference to the followingnon-limiting Examples.

EXAMPLE 1

Magnetic polymer beads were prepared in accordance with the process ofthe present invention using the following raw materials:

1. Water: This is the continuous medium in which the organic phase isdispersed and then reacted.

2. Gosenhol® GH 17: this is a high molecular weight polymericsurfactant, a polyvinyl alcohol, that disperses the organic phase in thewater as droplets.

3. Teric® N9: this is a low molecular weight surfactant that is added tofurther reduce the particle size of the dispersed organic phase.

4. Cyclohexanol: this is the major porogen: it is a solvent for themonomers, but a non-solvent for the polymer, and it promotes theformation of voids and internal porosity in the resin beads.

5. Deodecanol: this is the minor porogen.

6. Solsperse® 24000: it is a solid phase dispersing agent and is a blockcopolymer of poly(hydroxystearic acid) and poly(ethyleneimine).

7. Pferrox® 2228HC γ-Fe₂ O₃ : gamma--iron oxide (maghemite). This is themagnetic oxide that makes the resin beads magnetic.

8. DVB-50 (divinyl benzene): this is the monomer that crosslinks thebeads.

9. GMA (glycidyl methacrylate): this is the monomer that is firstpolymerised to incorporate it into the beads, then it is quaternized toplace quaternary ammonium groups into the beads, thereby creating theion exchange sites: ##STR1## 10. AIBN: this is the catalyst thatinitiates polymerisation when the mixture is heated above 50° C.

11. Trimethylamine: this is the amine that reacts with the epoxy groupof the glycidyl methacrylate to form quaternary ammonium ion exchangesites.

12. Hydrochloric acid: this is used to neutralise the high pH due to thetrimethylamine.

13. Ethanol: this is used as a rinse and as a wetting agent.

Method

Water (6.3 L) was charged to a 20 L reactor and the stirrer and nitrogenpurge started. Next Gosenhol® GH-17 (30 g) and Teric® N9 (15 g) wereadded, and the water phase heated to 80° C. to dissolve the surfactants.While the water was heating cyclohexanol (1755 g) was charged to aseparate stirred mix tank and the stirrer turned on. Dodencanol (195 g),SOLSPERSE® 24000 (63 g), Pferrox 2228 HC γ-Fe₂ O₃ (936 g),divinylbenzene (410 g), and glycidyl methacrylate (1541 g) were added inturn. This mixture was stirred and sonicated for one hour.Azoisobutyronitrile (8 g) was added and the mixture was stirred for afurther five minutes before adding it to the heated water phase. Theresulting dispersion was held at 80° C. (±5° C.) for two hours, duringwhich time polymerisation occurs and the solid resin beads (2.95 kg)were formed. The nitrogen purge is then stopped and the trimethylamineand the hydrochloric acid are added to aminate the resin. These twomaterials can either be pre-mixed (with great caution due to theexotherm), or added in such a way as to maintain the pH between 6 and 8.The reaction mixture is then held at 80° C. for three hours. The mixtureis then cooled to room temperature, and the beads separated from theexcess γ-Fe₂ O₃ by repeated cycles of washing, settling and decanting(the beads settle much faster than the free oxide particles). The resinbeads are then filtered, redispersed in ethanol, then filtered andwashed with additional ethanol, then acetone, and dried with an airstream. Photomicrographs of the polymer beads produced by this exampleare shown in FIGS. 1A and 1B. As can be seen, especially from FIG. 1Bwhich is a photomicrograph of cracked beads, the solid particles areevenly dispersed throughout the polymer beads.

The maghemite was well dispersed throughout the resin beads produced inthis Example.

Comparative Example 1

The materials and method of Example 1 were used to make 58 g of resin ona 300 g scale, the sole difference being that the dispersant for theγ-Fe₂ O₃, Solsperse 24000, was omitted from the preparation. After thepolymerisation and quaternization, fine, dark brown beads were obtained.However, when the beads were cracked open, their interiors were whiteand only the surfaces were brown. Photomicrographs of these beads areshown in FIGS. 2A and 2B. FIG. 2B is a photomicrograph of cracked beadsand, as can be seen, the γ-Fe₂ O₃ was only attached to the surface ofthe beads and not dispersed through the bulk. This means that the beadsare highly likely to lose γ-Fe₂ O₃ in service.

EXAMPLE 2

Magnetic macroporous weak acid cation exchanger beads are prepared inaccordance with the process of the invention. The suspensionpolymerization described in Example 1 was repeated with the glycidylmethacrylate replaced by an equal weight of ethyl acrylate. At the endof the polymerization sodium hydroxide was added to the aqueous phase(1.5 moles per mole of ethyl acrylate) and the mixture gently stirred at80 degrees. Samples were withdrawn at intervals and the beads washed bydecantation with water and ethanol as described in Example 1, thenpacked into a glass column fitted with a porous glass frit and elutedwith dilute hydrochloric acid to convert the sodium acrylate functionalgroups to acrylic acid groups. The beads were then dried in a vacuumoven. The unhydrolyzed poly(ethyl acrylate) beads contained 40.3% ironoxide by weight. After hydrolysis for 2 hours at 80 degrees the producthad a weak acid capacity of 2.1 milliequivalents per gram and contained40.2% iron oxide; after 7 hours' hydrolysis the capacity was 2.9 meq/gand the iron oxide content 38.8%.

EXAMPLE 3

Magnetic polymer beads were prepared in accordance with the process ofthe present invention using the following raw materials:

1. Water: this is the continuous medium in which the organic phase isdispersed and then reacted.

2. Gosenhol®GH 20: this is a high molecular weight polymeric surfactant,a polyvinyl alcohol, that disperses the organic phase in the water asdroplets.

3. Cyclohexanol: this is the major porogen: it is a solvent for themonomers, but a non-solvent for the polymer, and it promotes theformation of voids and internal porosity in the resin beads.

4. Toluene: this is the minor porogen.

5. Solsperse® 24000: it is a solid phase dispersing agent and is a blockcopolymer of poly(hydroxystearic acid) and poly(ethyleneimine).

6. Pferrox® 2228HC γ-Fe₂ O₃ : gamma--iron oxide (maghemite). This is themagnetic oxide that makes the resin beads magnetic.

7. KRATON® D1102: this is a low molecular weight rubber, incorporatedinto the organic phase to toughen the polymer beads.

8. DVB-50 (divinyl benzene): this is the monomer that crosslinks thebeads.

9. GMA (glycidyl methacrylate): this is the monomer that is firstpolymerized to incorporate it into the beads, then it is quaternized toplace quaternary ammonium groups into the beads, thereby creating theion exchange sites.

10. VAZO® 67: this is the catalyst that initiates polymerisation whenthe mixture is heated above 50° C.

11. Trimethylamine: this is the amine that reacts with the epoxy groupof the glycidyl methacrylate to form quaternary ammonium ion exchangesites.

12. Hydrochloric acid: this is used to neutralise the high pH due to thetrimethylamine.

Method

Water (2333 g) was charged to a 5 L reactor and the stirrer and nitrogenpurge started (Next, Gosenhol GH20 (10 g) was added, and the water phaseheated to 80° C. While the water was heating Toluene (130 g), DVB-50(130 g) and a first portion of Cyclohexanol (130 g) were charged to aseparate mix tank and the stirrer turned on. The Solsperse 24000 (21.84g) and the Pferrox 2228 HC γ-Fe₂ O₃ (325 g) were added in turn, then themixture was stirred and sonicated for 20 minutes to thoroughly dispersethe magnetic oxide. Kraton D1102 was then added and the mixture stirredfor a further hour to dissolve the toughening agent. Glycidylmethacrylate (520 g), the remaining Cyclohexanol (390 g) and the VAZO 67(2.65 g) were then added and the mixture was stirred for a further fiveminutes before adding it to the heated water phase. The resultingdispersion was then stirred and held at 80° C. for two hours. Thenitrogen purge was stopped and a mixture of trimethylamine (687 g; 25%w/w) and hydrochloric acid (294 g; 36% w/w) added, then the mixture wasthen stirred and held at 80° C. for a further three hours. The mixturewas then cooled and the resulting polymer beads cleaned as in Example 1.A photomicrograph of the beads is shown in FIG. 3A. FIGS. 3B and 3C arephotomicrographs showing the beads crushed between two microscopeslides. Some of the beads are broken revealing their interiors. Thisillustrates that the solid magnetic oxide is well dispersed throughoutthe beads, and the beads are qualitatively tougher than those ofExample 1. Further, the size distribution of the polymer beads wasrelatively narrow.

EXAMPLE 4

Magnetic polymer beads were prepared in the manner of Example 3, exceptthat the temperature of polymerisation was 70° C. Polymer beads similarto those of Example 3 were produced.

EXAMPLE 5

Magnetic polymer beads were prepared in the manner of Example 3, exceptthat the temperatures of polymerization was 90° C., and that the mixtureof monomers, porogens and magnetic oxide was gradually fed to the waterphase over sixty minutes. Polymer beads with excellent magnetic oxidedispersion and strength resulted, however the distribution of polymerbeads sizes were relatively broad.

EXAMPLE 6

Magnetic polymer beads were prepared in the manner of Example 3, exceptthat the initiator was Lauroyl Peroxide. The resulting polymer beadswere not homogeneous. In some instances the distribution of magneticoxide was acceptable however there was varying extents of separation ofthe magnetic oxide from the polymer matix. Some beads contained nomagnetic oxide.

EXAMPLE 7

Magnetic polymer beads were prepared in the manner of Example 3, exceptthat the initiator was Benzoyl Peroxide. While the resulting polymerbeads had acceptable magnetic oxide distribution, the beads had a veybroad size distribution, and many were irregular, rather than spherical,in shape.

EXAMPLE 8

Magnetic polymer beads were prepared in the manner of Example 3, exceptthat the amount of Solsperse 24000 was one third that in Example 3. Theresulting beads had a poor distribution of magnetic oxide, with internalregions that were white due to a lack of oxide, similar to ComparativeExample 1. There was much magnetic oxide not incorporated into thebeads.

EXAMPLE 9

Magnetic polymer beads were prepared in the mannner of Example 3, exceptthat the amount of Solsperse 24000 was three times that in Example 3.While the resulting polymer beads generally had acceptable magneticoxide distribution, the beads also frequently included smaller whitebeads that were free of oxide, and were fragile, rather than tough.

EXAMPLE 10

Magnetic polymer beads were prepared in the manner of Example 3, exceptthat the amount of Gosenhol GH20 was one third that in Example 3. Whilethe resulting polymer beads generally had acceptable magnetic oxidedistribution, the beads also frequently included smaller white beadsthat were free of oxide, but were tough, unlike Example 9.

EXAMPLE 11

Magnetic polymer beads were prepared in the manner of Example 3, exceptthat the amount of Gosenhol GH20 was three times that in Example 3. Theresulting polymer beads had good magnetic oxide distribution and weretough. However, the beads occasionally included smaller white beads thatwere free of oxide, but were hard and tough, unlike Example 9.

It will be appreciated that the invention described herein issusceptible to variations and modifications other than thosespecifically described. It is to be understood that the inventionencompass all such variations and modifications that fall within thespirit and scope.

We claim:
 1. A process for producing polymer beads of ion exchange resinincorporating solid particulate material, which process comprisesproducing a dispersion having a dispersed phase including one or moremonomers and the solid particulate material, and causing said one ormore monomers to undergo a polymerisation reaction to form said polymerbeads of ion exchange resin, wherein said dispersion further includes asolid phase dispersing agent for dispersing the solid particulatematerial in the dispersed phase and wherein said solid phase dispersingagent reacts with the at least one monomer to thereby become chemicalincorporated in said polymer beads of ion exchange resin.
 2. A processaccording to claim 1 wherein the dispersed phase is an organic phase. 3.A process according to claim 1 wherein the ion exchange resins areproduced from crosslinking monomers which are able to providecrosslinking points and/or functional monomers which are able to provideion exchange functional groups.
 4. A process according to claim 3wherein the crosslinking monomers are selected from the group consistingof the divinyl monomers divinyl benzene, ethyleneglycol dimethyacrylateor poly(ethyleneglycol)dimethacrylate or methylene bisacrylamide,ethyleneglycol divinylether and polyvinyl ester compounds having two ormore double bonds.
 5. A process according to claim 3 wherein thefunctional monomers are selected from the group consisting of glycidylmethacrylate, vinyl benzyl chloride, dimethylaminoethyl methacryalte,N,N-dimethylaminopropyl acrylamide and methacrylamide, vinyl pyridine,diallylamine, and their quaternized derivatives, N-vinyl formamide andits hydrolized derivatives.
 6. A process according to claim 3 whereinsaid functional monomers are present in a amount of from 10 to 99% byweight based upon the total monomers, said crosslinking monomers beingpresent in an amount of from 1 to 90% by weight based upon the totalmonomers and additional monomers may be present in a amount of up to 60%by weight based upon the total monomers.
 7. A process according to claim3 wherein said functional monomers are present in an amount of from 50to 90% by weight based upon the total monomers, said crosslinkingmonomers being present in an amount of from 10 to 50% by weight basedupon the total monomers and additional monomers may be present in anamount of up to 30% by weight based upon the total monomers.
 8. Aprocess according to claim 3 wherein total monomers are present in anamount of from 1.0 to 50% by weight of the mixture.
 9. A processaccording to claim 3 wherein total monomers are present in an amount offrom 5.0 to 30% by weight of the mixture.
 10. A process according toclaim 3 wherein the polymer beads of ion exchange resins are treated toactivate sites in the polymer beads of ion-exchange resins.
 11. Aprocess according to claim 10 wherein the polymer beads of ion exchangeresins are treated to by one of hydrolysis, amination andquatrinization.
 12. A process according to claim 1 wherein the dispersedphase further includes one or more porogens.
 13. A process according toclaim 12 wherein said porogens are selected from the group consisting ofaromatic compounds toluene and benzene, the alcohols butanol,iso-octanol, cyclohexanol, dodecanol, isoamyl alcohol and methyliso-butyl carbinol, the esters ethyl acetate and butyl acetate, thesaturated hydrocarbons n-heptane, iso-octane, the halogenated solventsdichloroethane and trichloroethylene, and plasticisers dioctylphthalateand dibutyl adipate, the polymers polystyrene and polyvinyl acetate; andmixtures thereof.
 14. A process according to claim 12 wherein saidporogens are mixtures of cyclohexanol with dodecanol or toluene.
 15. Aprocess according to claim 1 wherein said solid particulate material isa weighting agent.
 16. A process according to claim 15 wherein saidsolid particulate material is selected from the group consisting oftitania, zirconia, barite, cassiterite, silica, aluminosilicates, nickeloxide, copper oxide, zinc oxide and zinc sulphide.
 17. A processaccording to claim 1 wherein said solid particulate material is amagnetic material.
 18. A process according to claim 17 wherein saidsolid particulate material is selected from the group consisting ofγ-iron oxide (γ-Fe₂ O₃, also known as maghemite), magnetite (Fe₃ O₄) andchromium dioxide.
 19. A process according to claim 1 wherein said solidparticulate material ranges in size from sub-micron to 500 μm.
 20. Aprocess according to claim 1 wherein said solid particulate material isin the range of from 0.1 μm to 10 μm.
 21. A process according to claim 1wherein said dispersion further includes a stabilizing agent.
 22. Aprocess according to claim 21 wherein said stabilizing agent is selectedfrom the group consisting of polyvinyl alcohol, gelatine, methylcellulose or sodium polyacrylate.
 23. A process according to claim 21wherein said stabilizing agent is present in an amount of 0.01 to 5.0%by weight of the whole dispersion.
 24. A process according to claim 21wherein said stabilizing agent is present in an amount of 0.05 to 2.0%by weight, based on the weight of the whole dispersion.
 25. A processaccording to claim 1 wherein said dispersion further includes aninitiator.
 26. A process according to claim 25 wherein said initiator isselected from the group consisting of azoisobutyronitrile, benzoylperoxide, lauroyl peroxide and t-butyl hydroperoxide.
 27. A processaccording to claim 25 wherein said initiator is present in the range of0.01 to 5.0 wt % based on the total weight of monomers.
 28. A processaccording to claim 25 wherein said initiator is present in the range of0.1 to 1.0 wt % based on the total weight of monomers.
 29. A processaccording to claim 1 wherein the solid particulate material is presentin an amount of from 10 to 30% based upon the weight of the totalmonomers.
 30. A process according to claim 1 wherein the solidparticulate material is present in an amount of from 20 to 100% basedupon the weight of the total monomers.
 31. A process according to claim1 wherein said solid phase dispersing agent is present in an amount offrom 0.10 to 30.0% by weight of the solid particulate material.
 32. Aprocess according to claim 1 wherein said solid phase dispersing agentis present in an amount of from 1.0 to 10.0% by weight of the solidparticulate material.
 33. A process according to claim 32 wherein thepolymer beads of ion exchange resins are treated to a subsequent step.34. A process according to claim 1 wherein all the components of thedispersed phase are premixed and subsequently dispersed in a continuousphase.
 35. A process according to claim 1 wherein said dispersed phasefurther includes a toughening agent.